Ridiculously Easy Butterscotch Sauce

Ridiculously Easy Butterscotch Sauce
Adapted loosely from The Washington Post, who adapted it from The Perfect Cake
Yield: About 2/3 to 3/4 cup sauce
1/4 cup (4 tablespoons, 2 ounces or 1/2 stick) unsalted butter
1/2 cup packed dark or light brown sugar (I used dark)
1/2 cup heavy cream
1/2 teaspoon flaky sea salt (or 1/4 teaspoon regular salt), plus more to taste
1 1/2 teaspoons vanilla extract, plus more to taste
Melt butter in a medium heavy-bottomed saucepan over medium heat. Add the sugar, cream and salt and whisk until well blended. [A flat whisk works great here.] Bring to a very gentle boil and cook for about five minutes, whisking occasionally.
Remove from heat and add one teaspoon of the vanilla extract, stirring to combine and this is where, despite the simplicity of the recipe, you get to feel all “chef-y”. Dip a spoon in the sauce and carefully taste the sauce (without burning your tongue!) to see if you want to add additional pinches or salt or splashes of vanilla. Tweak it to your taste, whisking well after each addition. I ended up using a full teaspoon of flaky salt and the listed amount of vanilla to get a butterscotch sauce with a very loud, impressive butterscotch flavor but the strength of your vanilla and intensity of your salt may vary.
Serve cold or warm over vanilla ice cream, roasted pears or pound cake. The sauce will thicken as it cools. It can be refrigerated in an airtight container and reheated in a microwave or small saucepan.
To do ahead: This sauce will keep at least two weeks in an airtight container in the fridge.